Commercial biocides are used to control the growth of microorganisms in flowing or stagnant systems (piping, transit lines, tanks, cooling water and waste water systems) which can become fouled due to biofilm development. In many flowing aquatic systems, bacteria are able to adhere to a variety of surfaces (steel, glass, plastic). Bacterial attachment to surfaces is affected by several factors including surface charge and energy, hydrophobicity, nutrient availability, fluid flow and shear, microorganism type and temperature. As colonization progresses, microbes absorb nutrients from the flowing fluid, grow as an adhered biomass and produce extracellular slime. The fibrillar network of slime allows the cells to attach to each other and maintain successive populations on the adhering surface. The fouling biomass can eventually increase frictional resistance of fluid flow and in severe cases cause plugging of a tubular system. In addition, biofouled surfaces of metals undergo a progressive deterioration characterized by complex chemical and biochemical oxidation-reduction reactions in which bacteria (e.g. sulfate-reducing bacteria) can initiate or accelerate the corrosion process.
In studies of biofilm formation, McCoy et al (1981, Canad, J. Microbial. 27:910) and Ruseskca et al (1982, Oil and Gas J., March 8, pp 253-264) have described a continuous flow tubular recycle reactor for biofilm sampling (hereinafter referred to as the Robbins device) which can be placed as a bypass or slipstream into an existing flow system. The Robbins device has removable test surfaces (studs) for studying the development of biofilm growth and evaluating biocide effectiveness. The present invention is an improvement over the Robbins device, which suffers from several inadequacies, as will be described more particularly hereinafter.